This research is designed to yield insight into fundamental problems of inheritance concerned with structural organization of chromosomes of higher organisms and their mechanisms of synapsis, crossing over, crossover interference and anaphase assortment and distribution. Organisms are used which combine special qualifications for meaningful experimentation with genetic mechanisms nevertheless probably similar or identical to those of humans. Methods include microscopic observation at both light and electron levels, autoradiography and treatment of meiotic mutants and structurally aberrant material with physical and chemical agents.